1. Field of the Invention
This invention relates to a recording method using a recording liquid (hereinafter referred to as "ink"), and more particularly, to a multi-color recording method.
2. Description of the Prior Art
Ink jet recording is effected by generating and flying small droplets of an ink by various ink ejecting methods (e.g. electrostatic suction, application of mechanical vibration or displacement to ink using a piezoelectric element, or utilizing a pressure of bubbles formed by heating the liquid) and attaching a part or all of the small droplets to a receiving member such as paper and the like. Such a recording method gets much attention since the noise is little and high speed printing and multi-color printing are possible.
As an ink for ink jet recording, there is used mainly an aqueous ink from the standpoint of safety and printing suitability, and as a receiving member, there has been generally used, heretofore, plain paper. When recording is effected with a liquid ink, it is required in general that the ink does not blot and the printed letter is not blurred, and in addition, it is desired that the ink is dried as soon as possible after recording and does not stain the paper surface.
In particular, in the case of a multi-color ink jet recording where two or more inks of different colors are used, the following conditions should be satisfied:
(1) Even when an ink is rapidly absorbed to a receiving member and an ink dot overlaps another ink dot of a different color, the ink attached later neither mixes with the previously attached ink nor disturbs the ink dot, and does not flow out;
(2) an ink drop does not diffuse on the receiving member and the ink dot diameter does not become unnecessarily large;
(3) the shape of the ink dot is almost a true circle and the circumference of the dot is smooth;
(4) the density of each ink dot is high and the circumference of the dots is not blurred;
(5) the color of a receiving member is white and the contrast between the ink dot and the receiving member is large;
(6) the color of ink is not changed by the receiving member;
(7) the dimension of a receiving member does not change (e.g. wrinkle or elongation) before and after the recording; and the like.
Though it is understood that characteristics of the receiving member will play an important role to satisfy the above-mentioned requirements, conventional receiving members such as sized plain paper and coated paper can not meet the above-mentioned requirements.
In the case of the sized plain paper, diffusion of ink in the direction of the paper surface, a socalled blotting, can be suppressed, but ink can not be easily absorbed. As a result, there are the following drawbacks. The time required for fixing ink droplets is greater and, moreover, when ink droplets overlap, ink droplets of different colors are mixed or undesired enlarging of ink dots occurs or irregular ink dots are formed.
In view of the above-mentioned drawbacks, coated paper having a coating of a hydrophilic resin on the surface of the substrate paper has been proposed. However, the dye in the ink penetrates into the coated paper to a great extent and therefore, the diameter of the dot is liable to become large and the circumference of the dot is liable to blur.
Further, the shape and dimension of the paper change to a great extent depending upon the degree of hygroscopic property. In addition, the coating sometimes disadvantageously exfoliates from the substrate paper resulting in degradation of the recording quality, and further, it is a very difficult technique to form on the surface of a substrate paper a coating layer of uniform characteristics.